Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first image in a sequence of a displayscreen or portion thereof with transitional graphical user interfaceaccording to the claimed design; and,

FIG. 2 is a front view of a second image thereof.

The appearance of the transition is sequential from FIG. 1 to FIG. 2.The process or period in which an image transitions to another imageforms no part of the claimed design. The shading depicts a contrast inappearance.

The longer-dash broken lines illustrate an electronic device. Theintermediate-length broken lines illustrate the perimeter of a displayscreen. The remaining broken lines illustrate features within thegraphical user interface. The broken lines form no part of the claimeddesign.

CLAIM The ornamental design for a display screen or portion thereof withtransitional graphical user interface, as shown and described.